This invention relates to nickel electrode fabrication and, in particular, to improved techniques for achieving this fabrication.
In U.S. Pat. No. 4,659,379, assigned to the same assignee hereof, there is disclosed a method for fabricating a nickel electrode so as to realize reduced electrode creepage and increased sintering resistance. In the method of the '379 patent, a nickel alloy material is subjected to an oxidation procedure which results in the interior of the material comprising nickel metal having dispersed therein an oxide of the alloy and which further results in the exterior of the material comprising a nickel oxide layer. Following the oxidation procedure, the material is then reduced and sintered to convert the nickel outer layer to nickel metal, thereby forming a sintered porous component having a nickel exterior and in its interior a metallic nickel matrix throughout which is dispersed an alloy of the oxide.
The '379 patent teaches that the oxidant step can be carried out as a single step in which the nickel oxide outer layer and the inner metal with dispersed oxidized alloy are formed simultaneously or in multiple steps wherein the latter is formed in a first step and the former in a subsequent step, preceded by a particle diminution step. In the multiple step case, the '379 patent indicates that this can be accomplished by using an initial atmosphere comprised of a water vapor/hydrogen mixture, possibly diluted with nitrogen, or a carbon dioxide/carbon monoxide mixture. This initial atmosphere would then be followed by an atmosphere of air or pure oxygen. The patent further gives as an example of the conditions of the first step the use of an atmosphere of water vapor and hydrogen having a ratio of partial pressures of 100 to 1. This atmosphere is applied for about 10 hours at 950 degrees centigrade. Further, as an example of the second step, the patent calls for an atmosphere of pure oxygen applied for about 10 to 30 minutes. The patent also specifies that preferable conditions for the reduction/sintering step are a temperature in the range of 600 to 1,000 degrees centigrade and a period of time from about one-half to two hours.
While the method in the '379 patent results in a reduced amount of electrode creepage, researches have continued to look for still further procedures which can provide additional creepage reduction.
It is, therefore, a primary object of the present invention to provide an improved method of nickel electrode fabrication.
It is a further object of the present invention to provide a method of nickel electrode fabrication which results in reduced creepage during use of the electrode.